Thermophysical Characteristics of Lauric Acid/Polylactic Acid/MXene Composite Phase Change Materials: A Molecular Dynamics Study

Phase change materials (PCMs) have attracted significant attention from researchers due to their efficient energy storage properties, whereas the use of PCMs in energy storage has been restricted due to their low thermal conductivity and ease of leaking. This study selected lauric acid (LA) as the PCM, poly(lactic acid) (PLA) as the porous skeleton, and MXene as the thermally conductive reinforcing filler. Molecular dynamics simulation was employed to investigate the thermophysical properties of composite PCMs (CPCMs). Initially, physical properties such as diffusion coefficients and phase change temperatures of LA and different CPCMs were analyzed by simulation. Subsequently, the thermal conductivities of LA and different CPCMs were evaluated using the reverse nonequilibrium molecular dynamics (RNEMD) approach. The relationship between the molecular structure and thermal properties was analyzed using radial distribution function, end distance, and torsion angle assessments. Finally, the effect of MXene with various functional groups on interfacial thermal resistance (ITR) and thermal conductivity was investigated by analyzing the number of hydrogen bonds at the interface, the interaction energy, and the vibration power spectra. The simulation results showed that the introduction of PLA and MXene could increase the thermal conductivity of CPCMs, with the Ti3C2O2 system showing the highest thermal conductivity of 0.84 W/(m K) at 300 K, which was 237% higher than that of pure LA. This work analyzed the thermophysical properties of LA/PLA/MXene from a molecular point of view, which provided theoretical support and reference for the thermal conductivity enhancement of PCMs.